The present invention relates to sheet feeding devices, such as large capacity cassettes (hereinafter merely referred to as LCCs), adapted for use in sheet processing apparatus, such as image forming apparatus, to store therein a large number of sheets to be fed into the apparatus. The present invention further relates to image forming apparatus provided with such sheet feeding devices.
Conventional sheet feeding devices are positioned beside sheet processing apparatus for storing sheets of a size that is most frequently used therein. For example, LCCs adapted for use in copying machines as image forming apparatus generally have a capacity of approximately 2,000 sheets of A4-size plain paper placed in landscape orientation.
Designed for multipurpose use and to perform various functions such as of printing or facsimile communication, recent image forming apparatus tend to handle an increasing number of sheets of various sizes and types.
In light of the foregoing, there have been developed LCCs with a capacity of 4,000 or more sheets of various sizes. With 4,000 to 5,000 sheets of A3-size plain paper stored therein, such LCCs have a total weight of approximately 100 kg.
On the other hand, there has been strong demand for smaller and lighter image forming apparatus. Suppose an image forming apparatus is provided with an LCC. The LCC includes a sheet stacker for stacking sheets, and the sheet stacker is removable from a housing of the LCC. When the sheet stacker with a large number of sheets stacked therein is pulled out of, or pushed into, the housing, the impact of collision between the sheet stacker and the housing causes the image forming apparatus to vibrate or move. Such vibration or movement causes components inside the image forming apparatus to become loosely mounted or prevents the image forming apparatus from being maintained in a horizontal position.
To solve the foregoing problems, JP H11-208902A discloses an LCC that has an elastic member arranged in a housing so as to face a rear side surface of a sheet stacker. The elastic member is intended to cushion an impact of collision caused between the housing and the sheet stacker when the stacker is moved. JP 2003-267565A discloses an LCC that has a housing with an openable upper surface. The openable upper surface allows access to a sheet stacker from above, thereby eliminating the need to remove the sheet stacker from the housing for sheet replenishment or any other operation.
However, it is hard to determine an optimum shape, material, size, etc., for the elastic member in order to ensure that the elastic member cushions the impact of collision between the housing and the sheet stacker. Also, the construction as disclosed in JP 2003-267565A involves complicated arrangement of sheet feeding members and also makes it difficult to stack sheets in the sheet stacker without causing damage, such as bent corners, to the sheets.
A feature of the invention is to provide an LCC that ensures that a collision impact on a sheet processing apparatus is cushioned with a damping member provided in a sheet stacker. The damping member is adapted to act on the sheet stacker a damping force according to moving speed of the sheet stacker as being moved in and out of a housing of the LCC. Another feature of the invention is to provide an image forming apparatus that prevents components therein from becoming loosely mounted and is allowed to be maintained in a horizontal position.